Sunday, September 16, 2012

Heat by Wood: How Much Wood/Work/Time per Year

Many of us, particularly in cities, I think, rely on “black boxes” of magic for the conveniences we enjoy. We click a switch “over here” so that lights or heat or air conditioning or TVs turn on “over there”. When they fail to work, as they do in an era of “planned obsolescence” or a power outage, we either buy something new or enlist shaman-like experts called electricians or plumbers or auto mechanics or computer technicians to wave their magic wands.

Living off-grid in Alaska has made me more aware of all that goes into those things I used to take for granted. The article below outlines how much labor we expend to generate heat for ourselves, and outlines comparisons to alternative heat sources enjoyed by people who don’t live in the middle of a forest.

Since passing chemistry (barely), I hadn’t given a thought to British Thermal Units. In Alaska though, as you can imagine, that concept means a lot. We produce the heat for our cabin by chopping down birch trees that we then cut, age, and stack to stoke a small but efficient wood stove. How much wood do we need? How long does that take to acquire? How long does it last? How much heat does it produce?

The measurement for wood is a cord (4 x 4 x 8 feet). For dry birch, which is the available wood of choice for heating our cabin, this volume weighs about 3000 lbs (“green” wood weighs much more, about 4500 lbs). We store about 8 cords, or 32 x 4 x 8 feet and 24,000 lbs in our “wood corral.”